The World Patent Application WO 2009/121645 A1 describes a hydraulic vehicle brake system. The master brake cylinder of the hydraulic vehicle brake system includes a first pressure chamber and a second pressure chamber. At an end that widens relative to the brake pedal, the master brake cylinder also has an integrated pedal travel simulator, whose volume, which is fillable with brake fluid, communicates hydraulically via a simulator valve with a brake fluid reservoir. The volume of the pedal travel simulator, which is fillable with brake fluid, and the adjacent first pressure chamber are bounded by a rod/simulator piston in the form of a stepped piston.
In addition, the German Patent Application DE 10 2011 006 327 A1 describes a brake system of the brake-by-wire type that includes a master brake cylinder having two pistons that are movably disposed therein, one piston in the form of a stepped piston having at least two hydraulically active surface areas of different sizes, the stepped piston form producing an annular volume that can be filled with hydraulic fluid, respectively brake fluid. In response to the driver actuating the master brake cylinder in the brake-by-wire mode of operation, the smaller active surface area is effective for generating a braking torque at the vehicle wheels, and at a fallback level, i.e., the larger active surface area is effective when there is a malfunction that affects brake system operation; the smaller active surface area changing over to the larger active surface area as a function of a hydraulic pressure prevailing in a pressure chamber in the master brake cylinder (respectively, of the pedal force expended).